High power Free Electron Lasers (FEL) with power levels of 10 kW of infrared laser light have recently been demonstrated at the Thomas Jefferson National Accelerator Facility (TJNAF) in Newport News, Va. Although 10 kW of laser light is a substantial achievement, even higher levels of power would support advanced studies of biology, chemistry, and physics and enhance manufacturing technologies.
A linear accelerator (linac) supplies the FEL with electrons at relativistic speeds. For higher levels of FEL power, such as 1 MW, improvements are required in the accelerating structures in the linac. To achieve a power level of 1 MW in the FEL, electron beams in the range of 500 to 1,000 mA have to be accelerated in the linac supplying the FEL.
Successful operation of a linac at 0.5 to 1 amperes of current will require the accelerators to be based on superconducting technology. Additionally, Higher Order Modes (HOM) excited by the beams must be effectively damped to allow stable operation of the linac.
Therefore, one of the requirements for increasing the power level of an FEL to the 1 MW range is an accelerating structure capable of accelerating an electron beam in the linac to the level of 0.5 to 1 ampere and having sufficient damping to suppress the HOMs excited by the beams.